a) Field of the Invention
The present invention relates to a resistor forming method suitable for manufacture of LSI and the like, and more particularly to techniques of forming a resistor with a small occupied area and a high precision.
b) Description of the Related Art
Polysilicon resistors of a folded pattern, stripe pattern, and the like are widely used in an analog IC, analog/digital IC, and the like.
The width of a polysilicon resistor layer is required to be narrow in order to reduce an area occupied by the resistor. It is not easy to make a narrow polysilicon layer. As a polysilicon layer is made narrow, a precision of the width lowers and variations of resistance values become large.
A polysilicon resistor of a folded pattern, stripe pattern, and the like has a number of serially connected polysilicon layers of a bar shape. Each space between bar-shaped polysilicon layers is not used for forming the resistor and the area occupied by the resistor becomes large.